1. Field of the Invention
The present invention relates generally to microelectromechanical systems (MEMS), and more particularly to a protective packaging system and method whereby a one nanometer protective buffer is achieved using a monolayer of fullerene (C60) to establish the preferred spacing of two components while protecting the components from contacting each other.
2. Description of Related Art
Fullerene C60 
Fullerenes are crystalline forms of carbon and are a relatively new discovery. A method to produce the C60 fullerene, also known as xe2x80x9cbuckyballs,xe2x80x9d was first published by Kratschmer and Huffman in their article in Nature in 1990 (Vol. 347). The C60 form of fullerene, depicted in FIG. 1, is comprised of sixty carbon atoms arranged to form a hollow, soccer ball-like sphere. Heretofore, fullerene has been used as a lubricant and scientists are striving to find novel uses for this unique substance.
Tunneling Tip Applications
Microelectromechanical systems, or MEMS, are miniature devices which are seeing their use in a wide variety of experimental and commercial applications. Tunneling tip MEMS have been demonstrated as being feasible for use as accelerometers, pressure sensors, seismometers, thermal sensors, and microphones among others. In the manufacture of MEMS, an electrically biased tunneling tip is used to drive electrons from the tunneling tip to a metal conducting plate. A MEMS tunneling tip device of this type can include a pyramidal metal tip that faces an electrically conducting plate or diaphragm across the tunneling gap.
The tunneling tip is positioned either manually or electrically to a preferred distance of one nanometer from the plate, and a bias voltage induces a current between the tunneling tip and the conducting plate as electrons are transferred from the tip to the plate. When a current is detected, the tip is assumed to be positioned one nanometer from the conducting plate. Currently, the technology which is used to position the tunneling tip relies on electrical feedback from the tip-plate system, but such feedback is difficult to maintain during fabrication and assembly. Both the tunneling tip and the conducting plate are typically gold because of gold""s passive characteristics, but the use of gold poses a problem in positioning the tunneling tip with respect to the conducting plate. Accidental contact between the gold tunneling tip and the gold conducting plate can severely damage the components, in effect ruining the MEMS device. On occasion components which appear to have been successfully fabricated often were seen to have failed due to tip-plate crashing. Even where the tip is properly positioned relative to the conducting plate, the variation in sealing of the package is in many cases appreciable enough to cause the tip portion to be compromised thereby rendering the device inoperable.
The invention involves the deposition of a monolayer of C60 fullerene onto the conducting plate surface to protect the tip and conducting surface from premature contact (and subsequent damage). The Fullerene C60 molecule is approximately spherical and bonds weakly to neighboring molecules. A monolayer of fullerene has a thickness of one nanometer, automatically establishing the theoretical distance desired between the MEMS"" tunneling tip and the conducting plate. It would still be necessary to position the tip and diaphragm as in current fabrication process, but tunneling current would no longer be used to position the tip; instead, exploiting the electrical conductivity of C60, one simply monitors for contact between the tip and the fullerene film as indicated by the onset of electrical conductance between them. By monitoring the conductivity between the tip and the fullerene layer as the tip is brought in proximity, the surfaces can be brought together without risk of contacting the conducting surfaces. Once the tunneling tip is positioned at the one nanometer spacing, with only the monolayer of fullerene between the tunneling tip and the conducting plate, the monolayer of C60 can be broken down thermally and removed chemically leaving only the tunneling tip and the conducting plate at the ideal tunneling spacing. Alternately, the monolayer of fullerene can be left in place and the tunneling operation can occur directly across the fullerene cage.